1. Field of the Invention
This invention relates to motor vehicle speed sensors for differential assemblies. More specifically, this invention relates to an apparatus for sensing the rotational speed of the pinion shaft during all gear ratios.
2. Description of Related Art
Typical speed sensors consist of at least one magnet mounted in a protected environment on the stationary portion of the vehicle and a toothed or slotted metal rotor which rotates in response to the wheel movement. As the rotor teeth or slots pass the sensing device, variations in the magnetic flux produce a voltage the frequency of which is a function of the angular velocity of the wheel and the number of teeth or slots in the rotor.
In order to generate a voltage level which provides an accurate indication of the speed, the sensing device and the rotor must be accurately positioned with respect to one another during initial assembly and they must remain in this relationship even after extended periods of operation in which the components are subjected to road shocks and repeated vibrations. Therefore, most wheel speed sensors are mounted in the area of the wheel. However, such a location requires that additional care be taken not to damage the sensor during wheel maintenance.
The need exists for an improved speed sensing apparatus and method that provides speed sensing during all gear ratios.
The present invention provides an apparatus for sensing the rotational speed of the pinion shaft, and thus the axles, during all gear ratios.
It is object of the present invention to provide a wheel speed sensors having improved reliability and freedom from signal irregularities, combined with low cost. These factors are met in order for the system to provide enhanced economic benefits. Consequently, it is an object of the present invention to provide wheel speed sensors at minimum cost while providing maximum reliability and freedom from environmental problems.
It is a further object of the invention to provide wheel speed sensors that are essentially free of run out or deflections that could cause signal variation or create spurious signals.
In the speed-sensing system of the invention, a tone ring positioned on the ring gear flange is eliminated and the speed-sensing equipment is specially placed in the form of a thrust washer and/or slinger with a tone sensing ring disposed between the yoke and the inner race of the pinion shaft to avoid bending distortions of the ring gear under various dynamic load conditions.